There have already been developed various types of such compact transformer and one such compact transformer generally designated here as 11 is shown by way of example in FIG. 23 of the accompanying drawing, in which reference numerals 12, 13 designate identical E-shaped core elements made of ferrite. Leg ends of these core elements opposed to each other are abutted and fixed together so as to form respective closed magnetic circuits 14, 15. Reference numeral 16 designates a coil of low-tension side and reference numeral 17 designates a coil of high-tension. These coils are wound around central legs of the respective core elements 12, 13. It should be understood that there may be provided a certain gap between the respective central legs of said core elements 12, 13. Concerning the manner of coil winding, the respective coils 16, 17 are typically wound around tubular portions of associated bobbins into which the central legs of the respective core elements 12, 13 are inserted.
FIG. 24 is a circuit diagram of the photographic flash discharge device incorporated with the above-mentioned compact transformer 11. As seen in this circuit diagram, the compact transformer 11, oscillation transistors 18, 19, a resistor 20 forming a timer together with a capacitor 21, and a diode 22 altogether form a DC-DC converter adapted to boost DC voltage of a source battery 24 connected to the low-tension side and to provide output voltage used to charge a main capacitor 23.
The circuit arrangement of FIG. 24 further includes a neon lamp 25 adapted to be put on when the main capacitor 23 has been charged up to a predetermined voltage, a trigger circuit 26, a xenon discharge tube 27, stabilizing capacitors 28, 29, a diode 30 to protect oscillation transistors 18, 19 and a source switch 31.
FIG. 25 is a circuit diagram showing details of said trigger circuit 26. Referring to FIG. 25, upon closure of a trigger switch 32 in operative association with opening of the camera shutter, a trigger capacitor 33 is discharged through a primary coil of a trigger transformer 34 and a high voltage simultaneously generated across a secondary coil of said transistor 34 is applied to an exciting electrode of the xenon discharge tube.
It is important for the above-mentioned compact transformer 11 to minimize its outer dimension but to maximize its capabilities.
For example, when used in the photographic flash discharge device as shown in FIG. 24, the compact transformer 11 should effectively reduce a necessary space within the device for building-in of this transformer 11 and achieve a time for charging of the main capacitor 23 as short as possible. The compacet transformer 11 used in such application usually generates heat of a considerable high temperature and may often lead not only to dielectric breakdown of the transformer itself but also to heating of various circuit components therearound.
This problem of heat generation will be serious especially when the flash discharge lamp device is built in the photographic camera, since said compact transformer 11 must be incorporated together with the associated circuit components within a limited space available in the camera.